It will be the aim of this project to study in the developmental perspective the mechanisms of non-specific resistance to infection and intoxication. Particularly, emphasis will be placed on analysis in both ontogenetic and phylogenetic perspective of the development of capacity for organized inflammation, phagocytosis and digestion by polymorphonuclear neutrophils, leukocytes and heterophils; phagocytosis and digestion by eosinophils and macrophages. Natural experiments involving disturbances in these functions in both man and experimental animals will be analyzed. The development of capacity to detoxify such toxic proteins as bacterial endotoxins, venoms and naturally occurring toxins will be analyzed.